An explosion in a secret ammunition dump owned by a warlord in northern Afghanistan has left at least 28 people dead and 70 others wounded.

A government spokesman says the whole neighborhood around the ammunition dump has been destroyed.

He said the cause of the blast in a village in Baghlan province, 120 kilometers north of Kabul, is being investigated.

The arms depot belonged to one of Afghanistan's numerous militia commanders, who was officially disarmed but still kept ammunition hidden. The spokesman said the cache contained mortar bombs, artillery rounds and other ordnance.

Afghanistan is awash with weapons after decades of conflict. The government began a drive to disarm militias in 2003 but much ordnance remains uncollected.

There have been several blasts at arms depots in recent years but Monday's was the most deadly.